1. Field of the Invention
This invention relates generally to a light-emitting module, and more particularly, to a light-emitting module that emits light with equal luminance and saves energy.
2. Description of the Related Art
With the rapid development of modern technology, portable electronic appliances, such as mobile phones, personal digital assistants (PDAs) and notebook computers, have become more and more popular. These electronic appliances are generally provided with a keyboard construction, by which a user could input data or send instructions for the electronic appliance to run different programs. Moreover, in order to allow the user normal operations on the keys of the keyboard construction in dark surroundings, a light guide plate and a light source are typically configured within the keyboard module to illuminate the keys. The light guide plate reflects light rays coming from the light source, and as a result, the keys are illuminated. The user could then easily identify the position of each key and the symbol or number displayed on it; the user could press the keys to operate the electronic appliance even in dark surroundings.
Typically, the light source described above uses a light emitting diode (LED) light. The LED lights are distributed among the keys, and through the light guide plate, the light rays emitted by the LED lights are directed toward the symbols on the keys. To ensure that every key on the keyboard emits light with equal luminance, the amounts of LED lights may vary depending on the design of the keyboard. Usually, a computer keyboard requires at least six LED lights configured for the keyboard construction. Such configuration not only increases the manufacture cost, but also consumes more electricity or energy of the entire keyboard construction. In addition, distributing LED lights among the keys, in practice, is disadvantageous in that emitted light rays may have different luminances. This happens because the light rays emitted by an LED light fades gradually as the distance between the LED light and the key increases. When the LED light is lit up, it is clearly seen that the keys nearer the LED light are brighter, while the farther keys are not so bright. Although such configuration of light sources illuminates the keyboard, the light rays are not emitted with equal luminance, which may affect the user's visual perception.
For the related industries, it is therefore desirable to provide a light-emitting device for the keyboard construction that saves cost and energy and emits light with equal luminance.